"The greatest threat we face today is not terrorists; it is our own federal government," Mack says on his personal website. "If America is conquered or ruined it will be from within, not a foreign enemy."

In a 15-minute chat this week, Mack - or "Sheriff Mack," as he prefers to be called - reaffirmed these sentiments and went even further. He voiced his support for states to nullify federal laws they deem unconstitutional. He also called the U.S. government "universally corrupt."

The Southern Poverty Law Center - an Alabama-based nonprofit that tracks hate groups - has accused Mack of espousing "radical-right" views and trying to create a "nation of county sheriffs who believe the government is the enemy." Mack's group got some media attention when it compiled a list of more than 400 sheriffs who vowed not to enforce President Barack Obama's gun control measures.

Mack responded this week by calling the law center a "lying organization." He sued the center unsuccessfully in federal court last year.

Asked if he considered his sheriffs association a fringe group, Mack said, "If the Constitution is fringe, I guess we are."

Clarke said in a one-page statement that he does not want to get involved in the fight between Mack and the law center.

But he did say he fully intends to attend the sheriffs association convention in St. Charles, Mo. He is also listed as a speaker at the event, which runs from May 30 to June 1.

"I am extremely proud and humbled at the same time for this recognition by an association of my peers," Clarke said in a statement.

Then he added: "Have you ever been recognized by an association of writers as Journalist of the Year? If you ever are, and I read about it, I will congratulate you, not try to poop on your recognition."

"I loved how he conducted himself on TV," Mack said, referring to Clarke's contentious appearance on Piers Morgan's CNN show in January. The sheriff was defending his radio ad encouraging local residents to arm themselves because of severe cuts in law enforcement.

Mack said he was a little surprised to find out that Clarke runs for office as a Democrat, though he is not a member of the party. Mack said he was once a Democrat. More recently, he has been beaten badly when running as a Libertarian for a U.S. Senate seat and as a Republican in a Texas congressional primary last year.

This is not the first time Clarke has associated with those on the political extremes.

Earlier this year, the Milwaukee County sheriff did a lengthy interview on a syndicated show hosted by Alex Jones, best known for his anti-government views and conspiracy theories on everything from fluoride to the 9-11 terrorist attacks.

A spokesman for Milwaukee police Lt. Chris Moews, a Democrat running against Clarke next year, criticized the sheriff for these dalliances with the far right.

"It is astonishing that Sheriff Clarke won't distance himself from a nut that said, 'The greatest threat we face today is not terrorists; it is our own federal government,' and instead chooses to sling mud and come up with some silly political spin," said Moews campaign manager Sachin Chheda in an email. "It's time for Sheriff Clarke to go."